This invention relates to a glass fiber reinforced polyamide resin composition and moldings thereof, which can reduce torque at the time of melt kneading and also have excellent mechanical characteristics, vibration fatigue characteristics and external appearance of moldings.
Polyamide resins are used in various industrial fields by utilizing their excellent properties in terms of mechanical characteristics and heat resistance. Particularly, so-called reinforced polyamide resins in which mechanical characteristics are further improved by reinforcing with glass fibers are suitable used in the periphery of automobile engine hoods, because parts therein require high reliability as mechanism elements. These parts are expected to have excellent fatigue characteristics accompanied by vibration of the engine and good appearance in view of the design and reliability for satisfying demands by customers. However, since glass fibers of the glass fiber reinforced polyamide are apt to be exposed to the surface of moldings, and such a tendency becomes more significant as the parts become large, various methods have been proposed for the purpose of improving mechanical characteristics, vibration fatigue characteristics and appearance of moldings.
For example, with the aim of improving antifreeze liquid resistance, appearance and mold release property, JP-A-11-166119 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent application) proposes a reinforced polyamide resin composition which is produced by kneading a raw material comprised of a polyamide resin, glass fibers, an azine dye and an aliphatic bisamide compound and/or a higher fatty acid metal salt with glass fibers when the polymer is melted. However, this proposal does not describe acid value of the higher fatty acid metal salt, and there is a possibility of spoiling mechanical characteristics when the higher fatty acid metal salt having the acid value used in the Examples is added.
Also, with the aim of improving mechanical characteristics and vibration fatigue characteristics, JP-A-10-28863, JP-A-10-28865 and JP-A-11-226949 propose to increase the amount of graft polyamide existing in the interface between a polyamide and glass fibers. However, though mechanical characteristics and vibration fatigue characteristics are improved by such a complex, it has rather an opposite effect regarding the appearance of moldings due to a tendency to reduce fluidity at the time of molding as the amount of graft polyamide increases.
Also, with the aim of improving appearance of moldings, JP-A-3-100062 and JP-A-5-247341 propose a combination of glass fibers and an inorganic filler having a relatively small aspect ratio. However, though the appearance is improved by this method, vibration fatigue characteristics and mechanical characteristics are reduced.
In addition, an attempt has been made in JP-A-2-265965 to simultaneously improve mechanical characteristics and appearance of moldings by selecting polyamide 6 having relatively low melting point among polyamides and a copolymer of an aliphatic polyamide. However, it is difficult to improve vibration fatigue characteristics of the glass fiber reinforced composition by simply using these polyamides.
Also, JP-A-63-156856 and JP-A-56-30460 propose that the appearance is improved by controlling the aspect ratio and length of glass fibers existing in polyamide 46 and a polyester, but improvement of vibration fatigue characteristics cannot be expected from the glass fibers of such a shape.
On the other hand, it is general that a polyamide and a reinforcing material such as glass fibers are melt-kneaded using an apparatus such as an extruder, as a method for the production of a reinforced polyamide composition, but mixing of inorganic matter such as a reinforcing material becomes a cause of worsening productivity due to increased torque of the extruder.
Thus, regarding glass fiber reinforced polyamide resins, there is no method which can simultaneously improve mechanical characteristics, vibration fatigue characteristics and appearance of moldings, and it is inevitable to avoid increase in torque of an apparatus such as an extruder when a reinforced polyamide resin composition is melt-kneaded, so that concern has been directed toward a method which can satisfy these characteristics simultaneously and also can reduce torque at the time of melt kneading.
An object of the present invention is to provide a glass fiber reinforced polyamide resin composition and moldings thereof, which can reduce torque at the time of melt kneading and also have excellent mechanical characteristics, vibration fatigue characteristics and appearance of the moldings.
Other objects and effects of the present invention will become apparent from the following description.
With the aim of solving the above-described problems, the present inventors have conducted extensive studies and found as a result of the efforts that, when a composition prepared by combining a composition comprising a polyamide resin and glass fiber with a higher fatty acid amide compound, a higher fatty acid metal salt having a specified acid value and an azine dye at a specified ratio is used, torque at the time of melt kneading can be reduced and compositions and moldings having excellent mechanical characteristics and vibration fatigue characteristics and also excellent appearance of the moldings can be obtained. The invention has been accomplished based on this finding.
Accordingly, the invention relates to glass fiber reinforced polyamide resin compositions and moldings shown in the following items 1) to 12).
1) A glass fiber reinforced polyamide resin composition comprising:
(A) a polyamide resin; and, per 100 parts by weight thereof,
(B) from 20 to 170 parts by weight of glass fibers;
(C) from 0.01 to 5 parts by weight of a higher fatty acid amide compound; and
(D) from 0.005 to 5 parts by weight of a higher fatty acid metal salt having an acid value of 0.5 mg KOH/g or less.
2) The glass fiber reinforced polyamide resin composition according to claim 1, further comprising (E) from 0.01 to 5 parts by weight of an azine dye per 100 parts by weight of a polyamide resin (A).
3) The glass fiber reinforced polyamide resin composition according to claim 1 or 2, having a graft polyamide resin layer in an interface region between the polyamide resin (A) and glass fiber (B),
wherein the graft polyamide resin layer has a modulus of elasticity of dynamic viscoelasticity function as calculated from an amplitude of response stress signal and a phase difference between a stimulation distortion signal and a response stress signal, each measured by a scanning viscoelasticity microscopic method, of at least larger than 1 when regarding the modulus of elasticity of the polyamide resin as 1, and
wherein the graft polyamide resin layer has a thickness of from 1.0 xcexcm to 20 xcexcm.
4) The glass fiber reinforced polyamide resin composition according to claim 3, wherein said graft polyamide resin in the interface between the polyamide resin (A) and glass fibers (B) is present in an amount from 0.1 to 2 parts by weight per 100 parts by weight of the glass fibers (B).
5) The glass fiber reinforced polyamide resin composition according to claim 4, wherein said graft polyamide resin covers from 50 to 100% of the total surface area of the glass fibers (B).
6) The glass fiber reinforced polyamide resin composition according to claim 1 or 2, wherein the glass fibers (B) are surface-treated with a binder mainly comprising: a copolymer of maleic anhydride with an unsaturated monomer; and an aminosilane coupling agent.
7) The glass fiber reinforced polyamide resin composition according to claim 6, wherein the glass fibers (B) contain from 0.1 to 2 parts by weight of the binder per 100 parts by weight of the glass fiber.
8) The glass fiber reinforced polyamide resin composition according to claim 1 or 2, wherein the glass fibers (B) existing in the polyamide resin (A) has an aspect ratio (weight average fiber length/number average fiber diameter) of from 10 to 50, and the number average fiber diameter is within the range of from 8 to 15 xcexcm.
9) The glass fiber reinforced polyamide resin composition according to claim 1 or 2, wherein the polyamide resin (A) is at least one compound selected from polyamide 66, polyamide 6, polyamide 610, polyamide 612, copolymers and blends thereof, and copolymers and blends of polyhexamethylene isophthalamide (polyamide 6I) with polyamide 66 and optionally polyamide 6.
10) The glass fiber reinforced polyamide resin composition according to claim 1 or 2, wherein the polyamide resin (A) has a relative viscosity of from 1.6 to 3.7 as measured at 25xc2x0 C. and at a concentration of 1% in 98% sulfuric acid in accordance with JIS K6810.
11) A molded article which comprises a reinforced polyamide resin composition comprising:
(A) a polyamide resin; and, per 100 parts by weight thereof,
(B) from 20 to 170 parts by weight of glass fibers;
(C) from 0.01 to 5 parts by weight of a higher fatty acid amide compound; and
(D) from 0.005 to 5 parts by weight of a higher fatty acid metal salt having an acid value of 0.5 mg KOH/g or less.
12) The molded article according to claim 11, wherein the reinforced polyamide resin composition further comprises from 0.01 to 5 parts by weight of an azine dye (E), per 100 parts by weight of the polyamide resin (A).